$ E = \left[\begin{array}{rrr}1 & 1 & 0 \\ 2 & 1 & 0 \\ 1 & 2 & 2\end{array}\right]$ What is $ E^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}-1 & 1 & 0 \\ 2 & -1 & 0 \\ -\frac{3}{2} & \frac{1}{2} & \frac{1}{2}\end{array}\right]$